SecurID and garage door openers

[Joseph Ashwood]

----- Original Message ----- 
From: "Travis H." <solinym at gmail.com>
Subject: SecurID and garage door openers


> Similarly, how do those garage door openers with "rolling codes" work,
> given that the user may have pressed the button many times
> accidentally while out of range of the receiver?

My understanding is that since it is a purely monotonic counter it is plenty 
possible to do one of two things:
send {counter, data} instead of {data}, receiver stores last counter to 
avoid replays
have the receiver just keep counting forward for a while (not a good idea

> Is there any interest in reviewing the security of consumer-level
> devices?

I'd be willing to take a look at the protocol, but dissection is not my 
specialty.

> PS: How many cypherpunks does it take to open a garage door?
> http://www.cap-lore.com/Garage/

Currently, not very many, with proper designs openly published, not very 
many because not very many companies will use it. However, it could be a 
useful way for some cipherpunks to make some extra money. Anyone else up for 
it? and how about the car alarm?
                Joe 



---------------------------------------------------------------------
The Cryptography Mailing List
Unsubscribe by sending "unsubscribe cryptography" to majordomo at metzdowd.com